The suspension system of a vehicle (such as, a car, a truck, a motorcycle, or other wheeled vehicle) is the part of the chassis that supports the vehicle's frame, on which the vehicle's engine and body weight are carried. The vehicle's suspension system is required for absorbing and dampening shocks and maintaining the wheels in contact with the road. Suspension systems are designed to provide good riding dynamics, which are required to ensure vehicle safety and passenger comfort. These riding dynamics include road isolation, i.e., the vehicle's ability to smooth out travel on a bumpy road, as well as its ability to safely accelerate, brake and corner. For vehicles that are built specifically to handle on-road and off-road travel conditions, independent suspension of the wheels, which allows each individual wheel to move independently of the other wheels, is often used for better performance (in comparison to dependent suspension that has a rigid axle that connects a pair of opposed wheels, either the front wheels or the rear wheels). ‘Movement’ of the wheel in this context relates to vertical travel of the wheel relative to the vehicle frame. An engine or power source may be used to rotate one or more of the wheels, depending if the vehicle has front wheel drive, rear wheel drive, or four wheel drive. Typically, each set or pair of the driven wheels (front, rear, or both, respectively), receives the driving torque from the engine or power source via a drive shaft, which is split two ways by a differential, allowing each output axle to spin at a different speed. The differential is conventionally disposed in the middle, or offset from the middle (rearwardly, forwardly, upwardly, downwardly), between the opposite wheels. Two wheel axles extend from opposite sides of the differential towards the wheel hubs. The wheels, or wheel hubs, are typically supported by suspension arms, or equivalent mechanisms that allow vertical wheel travel, with suitable shock-absorbing and dampening features to complement the suspension performance. The length of the vertical travel of the wheel determines the inherent maximal performance of the wheel suspension mechanism. The greater the vertical travel of the wheel, the greater its maximal performance of its suspension capabilities. Extension of vertical wheel travel can improve, among other things, technical handling of the vehicle in off road drive by extending the time the wheels touch the ground, and extending the range of shock absorption, causing the work of the shock absorbers to be more gradual. However, as the driving torque is conveyed through the driving axle which extends from the differential to the wheel, and since the angular articulation of the wheel axle is limited, it is the length of the wheel axle that often determines to a great degree the maximal vertical wheel travel. Accordingly, longer wheel axles would provide greater vertical travel of the wheel.
One example of an attempt to provide longer wheel axles can be found at the website of PROFORMANCE® Motorsports, a differential carrier of PROFORMANCE® ultra narrow differentials into which internal CV (continuous velocity) joints of the opposed wheel axles are fitted deep inside, where the CV joint faces are only 40 mm apart.